This model is a beautiful pedagogical device for demonstrating the tendency of a moving belt to move to a larger diameter on the conical cylinder as the circular cylinder in rotated. The use of belt and pulley mechanisms was almost universal in the age of steam engine manufacturing to distribute power throughout the work stations. To prevent the belts from slipping off their pulleys and to avoid the use of pulley wheels with end face plates, the pulley wheels were spherically crowned. Any tendency of the belt to slip off would be self- corrected by the drift of the belt toward the larger diameter of the center of the wheel. This phenomenon was known at the time of Cambridge professor Robert Willis (1841). It also demonstrates the connection between mechanics and geometry because of the role that friction plays in the dynamics between the belt and the wheel surface.